This invention relates to an improved automotive voltage regulator system and, in particular, to isolation of the feedback network from spikes from diode commutation and voltage ripples from the alternator.
It is known to provide overvoltage protection circuits in automotive battery charging systems including a voltage regulator so as to prevent damage to voltage regulator components as described, for example, in U.S. Pat. No. 3,723,817 to Leonard, et al., U.S. Pat. No. 3,938,005 to Cummins, and U.S. Pat. No. 4,040,115 to Gruson. While these circuits are intended to protect transistor switches against voltage surge, they provide no benefit in isolating a positive feedback network from spikes due to diode commutation and voltage ripple from alternator current.
A feedback network associated with a voltage regulator provides current necessary for regulator switching. Feedback circuits are known as indicated for example, by U.S. Pat. No. 3,740,637. It has been found that spikes due to diode commutation and large ripple voltages at the alternator output terminals can cause feedback current to fluctuate which, in turn, causes improper switching of the regulator system resulting in damage to the battery. This is especially so in the case of large alternators and small batteries and/or long harnesses.